1. Field of the Invention
The present invention relates generally to fuse interruption indicators, more particularly to a fuse interruption indicator with visual and tactile physical attributes which are utilized to extract a fuse from a fuse receptacle.
2. Description of the Prior Art
Various electrical equipment, such as those used in the automotive industry, are generally protected from electrical current overload by disposable fuses. Such fuses are most often composed of a transparent housing with two conductive terminals joined by a meltable link.
When a fuse reaches overload, the meltable link melts due to high heat caused by excessive current moving through the fuse, this in turn interrupts the electrical circuit and the electrical equipment previously supplied with electricity ceases to function. At this point the equipment operator must inspect the fuse in order to discover if the failure is fuse related or equipment related.
Fuses are inserted into fuse receptacles which are generally integral components of the electronic equipment. Often, with complex machinery containing an assortment of electronic equipment, such as an automobile, a multitude of fuse receptacles are placed in one fuse receptacle location. If the fuse receptacles are adequately marked and sufficient light exists to observe the fuse receptacle markings and to determine fuse conditions through the transparent fuse housings, then the determination of fuse failure or equipment failure is easily made. However when situations provide less than ideal observation conditions, ascertaining, and ultimately exchanging, interrupted fuses with functioning fuses is both frustrating and tedious. Each of the numerous fuses appear and feel identical, and must be extracted and examined, often with the aid of additional lighting, before the interrupted fuse can be located.
As fuses require some force to remove, and are generally recessed within the fuse receptacle, it is often difficult to extract the fuse from its receptacle using only fingers due to the insufficient area of the fuse available for gripping. Fuses formed with handles or finger grips are impractical, in that the fuse receptacle location is usually configured with a minimum of space surrounding the fuse, and generally, a fuse receptacle cover is only a few millimeters from the top surface of the fuse.
The electrical equipment operator is generally required to posses a fuse removal tool, usually a two pronged device which the operator squeezes on the fuse housing and pulls with, in order to extract the fuse from its receptacle. The fuse removal tool must be kept in reasonable proximity to the electrical equipment, otherwise an inconvenient delay may be caused by locating, or acquiring the necessary fuse removal tool. Different types of fuses require differing types of fuse removal tools, consequently, equipment which utilizes differing fuse types requires the equipment operator to posses or acquire multiple fuse removal tools.
Inventors have created several methods for determining fuse continuity by utilizing fuse interruption indicators. Attempts have included thermal chemical methods such as U.S. Pat. Nos. 4,603,315 to Krueger et al. (1986) and 5,111,177 to Krueger et al. (1992) both of which coat the meltable link with a chemical composition which reacts to thermal conditions created by the meltable link in various stages of degradation and discolors the interior of a transparent housing. U.S. Pat. No. 4,127,837 to Botchart (1978) uses a thermal chemical reaction to remove a colored substance applied within the interior of a transparent housing. These methods require that the fuse housing be manufactured using a transparent material, which is more expensive than comparable opaque materials. In addition, these methods require sufficient light to examine the fuse and a fuse removal tool for easy fuse extraction.
Further attempts utilize light emitting visual sources such as U.S. Pat. No. 4,499,447 to Greenberg (1985) which shows a blade type fuse with a light source inserted into the fuse housing and wired in parallel with the meltable link. The light source is not activated and draws no current until the meltable link melts. This type of indicator is subject to reliability problems in that the electrical equipment must supply current to the fuse in order for the light source to function. Electrical equipment with a power outage will render this inoperative. Viewing the light source during bright light situations may be difficult and the light source is subject to vibration in vehicles and the filament or the wiring connection may fail. The indicator does not in any way facilitate fuse extraction.
Efforts have been made at mechanical indicators within the fuse housing. U.S. Pat. No. 3,665,361 to Williams (1972) shows a fuse with a meltable link used in conjunction with a previously biased spring member, which moves after the meltable link has melted. This has the disadvantage of requiring a transparent housing, which is costly, and requires that an additional light source be used in order to observe the fuse condition in low light situations. U.S. Pat. No. 3,824,520 to Knapp (1974) shows a polyphase fuse with large primary meltable links and a smaller secondary meltable link which restrains a spring loaded shaft. The spring pushes an end of the shaft out of the housing when the secondary meltable link melts. U.S. Pat. No. 5,113,169 to Frederiksen et al. (1992) shows a fuse with integrated internal arc snubbers which are spring loaded to move away from a transparent window which is costly and requires a light source in order to be observed in low light situations. These mechanical indicator inventions revolve around large commercial fuses which are simple to remove and so none of these inventions makes possible the utilization of the mechanical indicator to provide a method of fuse extraction.
U.S. Pat. No. 4,593,262 to Krueger (1986) shows a cylinder type fuse with a shaft orientated with an opening in one of the terminal end caps. In the event of the meltable link melting a spring pushes the shaft through the opening. This shaft may become encumbered by objects adjacent to the fuse receptacle, or may encounter another nearby fuse. As the indicator is expelled parallel to the fuse length, and consequently the fuse receptacle floor, it is difficult to use fingers to feel the indicator when it cannot be seen, and the indicator cannot be grasped to extract the fuse from the fuse receptacle.
In an attempt to combine an indicator with fuse removal, U.S. Pat. No. 4,475,283 to Borzoni et al. (1984) shows a fuse removal tool which uses an electrical circuit tester, however this device requires the use of specially configured fuses (U.S. Pat. No. 3,909,767), and the additional expense of the fuse removal tool itself, which must be stored in or near the electrical equipment. Placing the device upon a fuse causes a light source within the device to be wired in parallel with the meltable link, and fuses with the meltable link melted will cause the light source to draw current. The tester circuit utilizes an incandescent lamp which may become damaged and render the circuit tester inoperative. U.S. Pat. No. 5,002,505 to Heidorn (1992) shows a frame, which contains a light source, configured to fit piggyback upon a cylinder type fuse and subsequently the assembly is inserted into a fuse receptacle. The frame is formed to a substantial distance above the fuse housing to provide a graspable surface and retain the light source. This area of the frame will not fit within tightly configured fuse receptacle areas, as the frame will interfere with adjacent frames if an attempt is made to place this device in an area with a multitude of fuses, and the frame will interfere with the replacement of fuse receptacle covers. Once again the electrical equipment must supply current to the fuse in order for the light source to function and electrical equipment with a power outage will render this inoperative and viewing the light source during bright light situations may be difficult.
In a combination of fuse and fuse housing U.S. Pat. No. 3,696,316 to Kitagawa et al. (1971) shows a fuse which uses three conductive terminals, which are aligned with each other. This requires the specially configured fuse housing detailed in the same patent. The center terminal, and one adjacent terminal are joined by conductive members and a meltable link. The center terminal member is biased away from the other member and held in tension by a meltable link. The member is biased by a bend at its base and when the meltable link melts the center terminal member moves away from the other member and comes in contact with the third terminal. As the center terminal is the current carrier, this in turn shunts the current through the third terminal and activates an alarm circuit, which requires a power source, which may not be available at the time of inspection. The fuse housing has an opening through which the moved member may be seen, however this requires a light source and the moved member is below the housing surface and is not only difficult to feel, but as the moved member must draw current in order to activate the alarm circuit it would also be dangerous to touch, and so the moved member does not provide any method of fuse removal.
The current state of the art in the fields of fuse interruption indicators and fuse removal has not produced a fuse interruption indicator which is capable of providing a self contained fuse extraction method.